Unit 5: Linking Processes Driven By Internal and External Energy Sources

Unit 5 Learning Goals

By the end of this unit, students will be able to:

• Model the collaborative process of investigative Earth science.
  
• Describe how Earth processes are the result of energy flowing and mass cycling within and between Earth's systems.
  

Unit 5 Learning Objectives

To achieve that learning goal, students will meet the following objectives:

• Objective 5-1. Students will work collaboratively in groups to collect and interpret data, and to communicate results (including presentation of ideas via whiteboard to the larger group).
• Objective 5-2. Students will describe and illustrate energy transfer processes within and between Earth systems.
• Objective 5-3. Students will explain a viable Earth material transfer scenario using a rock cycle diagram that shows linkages between above-surface processes (erosion and sedimentation) and below-surface processes (lithification, metamorphism, melting).
• Objective 5-4. Students will describe/illustrate the energy sources required to create sediment from a metamorphic rock.
• Objective 5-5. Students will describe/illustrate the energy sources required to create a metamorphic rock from a sedimentary rock.
• Objective 5-6. Students will explain how mountainous areas with high rainfall might experience greater uplift than areas with lower rainfall (this requires previous experience with isostasy).

This unit is the fifth and final part of a module on surficial processes for an introductory geoscience content course that is aimed primarily at pre-service teachers. This type of course is common at state and regional schools with large teacher preparation programs. Students in these courses generally are not very strong in science and are often science-phobic. This activity is designed to take two hours.

The ideal class size is 24 students or fewer, as students work in small collaborative groups (ideally 3 students) with a faculty member acting as a facilitator. This activity would be difficult to adapt to a large lecture class.

Students will need a workspace for this group work, and groups will occasionally interact via discussion with the rest of the class.

Students will need to have prior understanding of density, as well as isostasy. They need this understanding of isostasy to understand the response of mountains to the removal of material (i.e., thinning of the crust). Students also should have prior experience with the formation of igneous, metamorphic, and sedimentary rock. This activity should ideally follow a unit on rocks and a unit on plate tectonics.

This unit offers a version of the activity that utilizes an energy diagram, which can be used to describe the way that energy is transformed and transferred during processes. Read more about the energy diagram and the benefits of its use.

In this activity, students take what they have learned from previous activities on surficial processes (hydrologic cycle, stream tables, and real-world stream profiles) and link them to internally driven processes (plate tectonics, rock cycle). Students will work in groups of three to answer general questions on the student activity sheet. These questions guide them to a more in-depth understanding of pathways in the rock cycle, associated energy transfers, and the interaction between the hydrologic cycle and plate tectonics/rock cycle. Students collaborate as they answer questions, and once students have been guided to a particular point of understanding, the activity sheets ask them to write their thoughts on a whiteboard and share with the rest of the class.

In the "Initial Ideas" segment, students answer content questions that relate to the major learning objectives of this activity (rock cycle pathways/interaction with hydrologic cycle/energy transfers). The goal is to surface all ideas without any attempt to correct misconceptions. These initial ideas are recorded by students, and can be used as a way to compare what they know at the end of the activity with what they thought at the beginning.

Questions to ask students to solicit their initial ideas:

• Where does the energy come from to transport sediment in a stream? Go as far back to the ultimate energy source as possible and explain your reasoning.
• What changes might happen to sediment if it piles up at the end of the river and gets deeply buried (many kilometers) for millions of years? What is the source of energy that is ultimately responsible for those changes? Explain your reasoning.
• Does the hydrologic cycle play a role in the rock cycle? Explain your thinking.
  
• Could the removal of many kilometers of rock from a mountaintop by erosion affect any of Earth's internal processes? Explain your reasoning.

Part 1 links the sediments that students have worked with in Activity 1 with their ultimate fate in the rock cycle. Students are asked to think how the sediments are generated (from rock that has been exposed at the surface) to what happens to them as they are buried and turned into metamorphic rock. At the end of Part 1, students are asked to look at a schematic diagram and specifically describe how the hydrologic cycle interacts with the rock cycle.

Part 2 has students map out the energy transfers that occur during the hydrologic cycle as well as during the rock cycle. Students are led to the understanding that the hydrologic cycle is driven by energy from the Sun, whereas much of the rock cycle (the below-ground part) is driven by Earth's internal energy (thermal energy from Earth's original formation and radioactive decay). The role of gravity is implicit, but is not directly addressed.

Part 3 is only in the energy diagram version, and asks students to create their own rock cycle pathway that sediment starting at the surface (from a flood in their hometown), might traverse. Students are asked to think about energy transfers along that pathway, as well as interactions between plate tectonics and the hydrologic cycle. The role of gravity is implicit, but students are not asked to quantify energy interactions related to gravity. Read more about the energy diagram.

The homework is a presentation of how erosion and removal of sediment from a mountainous region promotes uplift. The reading also presents the debate that surrounds the question of the most important driver for developing mountain ranges: climate or plate tectonics. The associated questions (on a separate student worksheet) can be used as a summative assessment.

• How Erosion Builds Mountains, by Mark Brandon and Nicholas Pinter, from Scientific American. The entire article can be read online with this link; if you or your institution has a subscription to Scientific American, however, you can access a PDF with all of the illustrations and make that available to your students.
• Activity 5 Homework Reading Student Question Sheet (Acrobat (PDF) 76kB Nov21 14)

Summarizing questions also provide the summative assessment material for the activity.

Materials

• Student worksheet (no energy diagrams) (Microsoft Word 2007 (.docx) 490kB Jan11 15)
• Unit 5 Key (no energy diagrams -- private instructor-only file
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• Student worksheet with energy diagrams (Microsoft Word 2007 (.docx) 567kB Jan11 15) - Read more about the energy diagram
• Unit 5 Key (with energy diagrams) -- private instructor-only file
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• Homework - student worksheet (Microsoft Word 2007 (.docx) 121kB Nov21 14)
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Students will work in small groups (ideally 3). Each group needs:

• A whiteboard (3' x 3' is usually good; it should be large enough so that the rest of the class can see what is written on the whiteboard when the group presents).
  
• Multiple colors of whiteboard markers.
  
• Cloth to clean off the whiteboards.
  
• A workspace for group work. These groups will interact via discussion with the rest of the class.
  

This unit is particularly focused on facilitated discussions. The role of the teacher is to facilitate only, and to avoid directly providing answers. The activity sheets are designed so that students should reach scientifically sound conclusions on their own. If they do not, the facilitator can guide the discussion to address any remaining misconceptions. This facilitated discussion is where much of the learning takes place or is solidified.

However, this unit can be challenging because the questions focus more on thought experiments and combining and applying what they have learned through experiments and data analysis in previous units to more abstract ideas and concepts.

Students must be encouraged often to read what is in the activity sheets and not look to the teacher to tell them what to do. Students must also be encouraged to write down their answers whenever they encounter a prompt. Skipping answers may lead to misconceptions or misunderstandings. Skipping answers also denies the students the opportunity to later reflect on their thought processes as they learn the material.

Formative assessment occurs via the following:

1. Facilitator listening in on group discussions of specific prompts to make sure that students are on the right track/holding productive conversations.
2. Facilitator listening in on class discussions of specific prompts.
3. Quality of individual student answers to specific prompts in the activity sheet.

Summative assessment occurs via the following:

1. Written answers to the summarizing questions.
2. Homework.
3. Written questions in an exam format.

Unit 5 assessments:

Assessable objectives are in normal font, and the writing/discussion prompts that assess those objectives are in italics:

• Students will be able to work collaboratively in groups to collect and interpret data, and to communicate results (including presentation of ideas via whiteboard to larger group).
• Formative and Summative Assessment: facilitator assesses quality of discussions both within and between groups. Are students collaborating effectively? Is discourse productive? Are higher order thinking skills being employed? Do students learn by interacting with their peers?

• Students will be able to describe and illustrate energy transfer processes within and between Earth systems.
• Formative Assessment:
• Unit 5, Part 2, Question 1. Review the energy transfer that occurs as water evaporates from a large body of water, and provide an explanation for that transfer.
• Unit 5, Part 2, Question 2. Now describe the energy transfer that occurs as that evaporated water condenses and falls out as precipitation. What would happen to the water in this cycle if the Sun did not continuously supply energy input?
• Unit 5, Part 2, Question 3. Map the energy transfer that occurs during that erosion process.
• Summative Assessment
• Unit 5, Summarizing Questions 1 and 2, 6
• Where does the energy come from to transport sediment in a stream? Go as far back to the ultimate energy source as possible and explain your reasoning.
• What changes might happen to sediment if it piles up at the end of the river and gets deeply buried (many kilometers) for millions of years? What is the source of energy that is ultimately responsible for those changes? Explain your reasoning.
• Describe a hypothetical rock material transfer pathway as follows: You live on the banks of a medium-sized river. The river floods during high rains. When the water finally recedes, there is a new layer of fine-grained sediment everywhere in your neighborhood. Using the rock cycle diagram and a whiteboard, your group should describe a hypothetical rock cycle pathway for that sediment that traverses at least one time through the rock cycle. Make sure you describe interaction with the hydrologic cycle and plate tectonics. Write down your resulting pathway below and make sure you include any required energy transfers.

• Students will be able to explain a viable Earth material transfer scenario using a rock cycle diagram that shows linkages between above-surface processes (erosion and sedimentation) and below-surface processes (lithification, metamorphism, melting).
• Formative Assessment:
• Unit 5, Part 2, Question 8. Brainstorm below what other things happen to a rock as it traverses the rock cycle.
• Summative Assessment:
• Unit 5, Summarizing Questions. . . . Describe a hypothetical rock material transfer pathway . . .
  

• Students will be able to describe/illustrate the energy sources required to create sediment from a metamorphic rock.
• Summative Assessment: Energy diagram from Part 2, Question 5 in worksheet: Map this energy transfer as a sedimentary rock receives thermal energy to be turned into a metamorphic rock. Provide an explanation.

• Students will be able to describe/illustrate the energy sources required to create a metamorphic rock from a sedimentary rock.
• Summative Assessment: Energy diagram from Part 2, Question 3 in worksheet: Map the energy transfer that occurs during that erosion process. The receiver object and its type of energy have been done for you. Provide an explanation of that energy transfer.

• Students will be able to explain how mountainous areas with high rainfall might experience greater uplift than areas with lower rainfall (this requires previous experience with isostasy.
  • Summative Assessment
  • Unit 5, Summarizing Question 5. The northern Andes mountain range and the mountains of southeastern Alaska are both large mountain ranges that are actively uplifting. Based on your homework reading, and given the difference in climate between the two (the northern Andes are desert, southeastern Alaska is very rainy), which mountain range would you expect to be rising faster? Explain your reasoning.
  • Unit 5, Homework: Homework prompt, How do feedbacks between tectonics, erosion, and climate processes interplay to influence mountain building?

• The figure in question 8 of the student activity sheet comes from the Reynolds textbook, Exploring Geology (Reynolds, et al. 2010. McGraw Hill, ISBN: 007337668x).
• The second figure in question 9 comes from the Geological Society of London's online unit about the rock cycle. Permission to reuse has been granted by the Geological Society of London.
• The reading for the homework is How Erosion Builds Mountains, by Mark Brandon and Nicholas Pinter, from Scientific American.
• Student materials for this activity